Coordination scheduling of metal materials for multiple lines in cold rolling area is an important part in the production operations for metallurgic enterprises. The effectiveness of the coordinated schedule has directly relationship on the stability of equipments and the operation efficiency in the multiple production lines in cold rolling area, and, on the quality of the final product and the production cost.
Taking the steel plant as an example, the cold rolling area comprises multiple production stages, such as, acid pickling, acid rolling, continuous annealing, hot galvanizing, hot galvanizing and aluminizing, finishing, electro-tinning, crosscutting, rewinding and etc. The hot rolled coils must pass the continuous acid pickling line to clean the iron oxide on the surface of the strip steel so as to perform cold rolling operation and the consequent surface processes smoothly. The hot rolled coils will be processed to be cold rolled coils in acid-rolling line, which can be directly sold, however, cold hardening caused by continuous cold deformation will lead to the increasing the strength and hardness of the coils and reducing the toughness, consequently, deteriorating the stamping characteristic. In order to improve the mechanical characteristic of the coils, the coils need to be annealed to softening the steel, smooth the surface, reduce the hardness, get a better resistance against deformation and crack, then a uniform distribution of structures and composites and a better performance of the material will achieve. In addition, the annealed coils also pass the electro-tinning or galvanizing line to form a firm, bright, compact, uniform and continuous alloy coating, which will realize good anti-corrosion and tarnish resistance characteristics. The tin-plated coils can be sold after being cut crossly according to the orders. FIG. 1 shows the arrangement of the respective production lines in the cold rolling area. The coordinated coil scheduling among multiple lines in cold rolling area has the features including multiple production lines arranged in parallel and in series concurrently, complex logistics, existence of both direct flows and cross flows simultaneously. Further, the coils are processed continuously in each production line, the processing of the coil cannot be started in the downstream production line until it is finished in the upstream production line, thus, the coil will be reprocessed or become wasted material, if its terrible defect incurred in the upstream production line is not be repaired in the downstream production line. Therefore, it must be guaranteed that the production in each production line is stably, and every product must be processed precisely in each line, so as to satisfy the customers' requirements. Reasonable coordinated coil schedule of multiple lines can equilibrate the production rhythm of the upstream and downstream of production lines in order to keep the production in each production line continuously and unblocked, reduce the changeover times, and keep the reasonable utilization of the production capacity and stably production in each production line.
Currently, the coil schedules in acid rolling, continuous annealing, hot galvanizing, hot galvanizing and aluminizing are made by the planner in each production line and the coordinated planner, in practice. The coordinated planner determines the production volume in each line per day, based on information such as the orders' requirements, the production capacity, the current state of lines and the coils in inventory etc. The planner in each production line determines the coil schedule based on the determined production volume in the lines each day. However, the practical production conditions are various, and often involve several decision makers, so that the current manual planning method could not effectively coordinate the production rhythms among the lines and determining the schedule with good performance, thus causing conflicts among the lines and increasing the changeover times, which couldn't guarantee the production stability and the quality of the product. On the other hand, the manual plan is strongly dependent on the personal experience of the planner, and the planner in each production line makes the coil schedule according to the scheduling requirements in the respective line. Each line may have different scheduling requirements to be taken into account thus causing conflicts between the coil schedules in different lines. If a coil schedule is made with only consideration of the scheduling requirements of a line, other lines may be negatively influenced and suffer from frequent changeover and material shortage, resulting in a high changeover costs. Therefore, it is important to determine the coil schedule for each production line in cold rolling area in a view of whole supply chain to coordinate coil schedules comprehensively, so as to optimize the overall production effect of all the lines in the cold rolling area.